OMG I figured it out! The problem was actually starting even before the electricity arrived within my house! I live in the south west of france which was hit by a huge storm this weekend. The power cut off at least 3 times this weekend. Once the power was finally put back on, I thought it was okay to use my pc. I couldnt have been more wrong. Even though the power was put back on, it wasnt at full throttle. the power company (edf) was still rewiring the network as it was almost completely destroyed in our region (from perpignan to the west coast). Anyway, they'd put it back on, but only in limited strength. That way ppl could have their lights on, but every power outlet in the house was only giving about half of what it should have been. end result was having what looked like a faulty power supply, when infact it was just that, but on a higher level. I've had the pc shut off only once today, and have gta4 up and running on windows 7. I guess for some this would have been too obvious, but honestly I thought when the powers on, its on. guess when major storms destroy lots of the electrical network, its not quite that simple. One of the big clues for me was that while we had power in the house, none of the street lights were on. anyway, hope that helps anyone living through the same situation. It wasnt windows 7!